影响母猪利用率的原因分析

综合1990～1993年我场所有淘汰母猪(112头)资料记载,进行归类分析,可以看出影响母猪利用率的因素主要为四大类,即母猪繁殖障碍(包括母猪低产)、产科病、四肢病及其他因素(包括有恶癖、疾病及死亡等),占淘汰母猪总数比例分别为:54.5%、18.8%、9.7%、17.0%.现将具体情况予以分析;以利今后生产中能够及时有效地采取措施,减少因此而引起的母猪年均生产力(包括全场平均每头母猪年产胎次、产仔率等)的下降,同时有利于有的放矢地进行药物及饲养管理等的综合处理,减少因不正常因素而淘汰的母猪.

Research Advance on Influencing Factors of Crop Water Use Efficiency

The research advance on the influencing factors of crop water use effi-ciency （WUE） was reviewed in this paper. Based on the discussion on the conno-tation of crop WUE, the influencing factors of crop WUE, such as crop, environ-ment, chemicals, cultivation measures, cropping systems, etc, were elaborated. A-mong them, the species and varieties of crop, soil and chemicals were discussed in detail.

Fixed Ammonium in Major Types of Paddy Soils in Hunan Province, China

The contents, affecting factors, seasonal changes and availability of fixed ammonium in major types ofpaddy soils derived from different parent materials in Hunan Province, China, were studied using the Silva-Bremner method by laboratory and pot experiments. Results showed that the content of fixed ammoniumin the plough horizons ranged from 88.3 mg kg-1 to 388.1 mg kg-1, with 273.2 ± 77.7 mg kg-1 on average,accounting for 11.2% of total soil N on average. Content of fixed ammonium decreased in the order of newlylacustrine clayey paddy soil ＞ alluvial sandy paddy soil ＞ purple clayey paddy soil ＞ newly alluvial sandypaddy soil ＞ yellow clayey paddy soil ＞ reddish-yellow clayey paddy soil ＞ granitic sandy paddy soil. Therewere four distribution patterns of fixed ammonium in the profiles to 1-m depth, i.e., increase with the depth,decrease with increasing depth, no distinct change with the depth, and abrupt increase or decrease in somehorizon. Percentage of fixed ammonium in total N increased with the depth in most of the soils. Fixationof NH4+ by soil was higher at 30 ℃ than at 20 ℃ and 40 ℃, and continuous submergence benefited thefixation of NH4+ in newly alluvial sandy paddy soil, purple clayey paddy soil and alluvial sandy paddy soil,while alternating wetting and drying contributed to the fixation of NH4+ in yellow clayey paddy soil mostly.Fixed ammonium content in the test paddy soils was significantly correlated with ＜ 0.01 mm clay content(P ＜ 0.05), but not with ＜ 0.001 mm clay content, total N, organic N and organic matter. Fixed ammoniumcontent varied with rice growth stages. Application of N fertilizer promoted fixation of NH4+ by soil, and Nuptake by rice plant promoted release of fixed ammonium from the soil. Recently fixed ammonium in paddysoil after N fertilizer application was nearly 100% available to rice plant, while native fixed ammonium wasonly partly available, varying with the soil type and rice type.

Suppression of glutamate synthase genes significantly affects carbon and nitrogen metabolism in rice (Oryza sativa L.)

Rice (Oryza sativa) glutamate synthase (GOGAT,EC 1.4.1.14) enzymes have been proposed to have great potential for improving nitrogen use efficiency,but their functions in vivo and their effects on carbon and nitrogen metabolism have not been systematically explored.In this research,we analyzed transcriptional profiles of rice GOGAT genes using a genome-wide microarray database,and investigated the effects of suppression of glutamate synthase genes on carbon and nitrogen metabolism using GOGAT co-suppressed rice plants.Transcriptional profiles showed that rice GOGAT genes were expressed differently in various tissues and organs,which suggested that they have different roles in vivo.Compared with the wild-type,tiller number,total shoot dry weight,and yield of GOGAT co-suppressed plants were significantly decreased.Physiological and biochemical studies showed that the contents of nitrate,several kinds of free amino acids,chlorophyll,sugars,sugar phosphates,and pyridine nucleotides were significantly decreased in leaves of GOGAT co-suppressed plants,but the contents of free ammonium,2-oxoglutarate,and isocitrate in leaves were increased.We conclude that GOGATs play essential roles in carbon and nitrogen metabolism,and that they are indispensable for efficient nitrogen assimilation in rice.

Effects of Different Biochars on Pinus elliottii Growth,N Use Efficiency,Soil N_2O and CH_4 Emissions and C Storage in a Subtropical Area of China

Intensive management of planted forests may result in soil degradation and decline in timber yield with successive rotations. Biochars may be beneficial for plant production, nutrient uptake and greenhouse gas mitigation. Biochar properties vary widely and are known to be highly dependent on feedstocks, but their effects on planted forest ecosystem are elusive. This study investigated the effects of chicken manure biochar, sawdust biochar and their feedstocks on 2-year-old Pinus elliottii growth, fertilizer N use efficiency （NUE）, soil N20 and CH4 emissions, and C storage in an acidic forest soil in a subtropical area of China for one year. The soil was mixed with materials in a total of 8 treatments： non-amended control （CK）; sawdust at 2.16 kg m^-2 （SD）; chicken manure at 1.26 kg m^-2 （CM）; sawdust biochar at 2.4 kg m^-2 （SDB）; chicken manure biochar at 2.4 kg m^-2 （CMB）; 15N-fertilizer alone （10.23 atom% 15N） （NF）; sawdust biochar at 2.4 kg m^-2 plus lSN-fertilizer （SDBN） and chicken manure biochar at 2.4 kg m^-2 plus 15N-fertilizer （CMBN）. Results showed that the CMB treatment increased P. elliottii net primary production （aboveground biomass plus litterfall） and annual net C fixation （ANCF） by about 180% and 157%, respectively, while the the SDB treatment had little effect on P. eUiottii growth. The 15N stable isotope labelling technique revealed that fertilizer NUE was 22.7% in CK, 25.5% in the NF treatment, and 37.0% in the CMB treatment. Chicken manure biochar significantly increased soil pH, total N, total P, total K, available P and available K. Only 2% of the N in chicken manure biochar was available to the tree. The soil N20 emission and CH4 uptake showed no significant differences among the treatments. The apparent C losses from the SD and CM treatments were 35% and 61%, respectively; while those from the CMB and SDB treatments were negligible. These demonstrated that it is crucial to consider biochar properties while evaluating their effects on plant growth and C sequestration.